Calculating machine



April 29 1952 J. R. nEscH ETAL cALcuLATING MACHINE 11 Sheets-Sheet l Filed March 20, 1940 'Joseph R. Desch and Robert E. Mumma Inventors By /ML M April 29, 1952 J. R. DEscH ETAL CALCLATING MACHINE 11 Sheets-Sheet 2 Filed Maich 20, 1940 Joseph R. Desch and Robert E. Mumma Inventors By M Their Attorney April 29, 1952 J. R. DEscH ETAL CALCULATING MACHINE 11 Sheets-Sheet 5 Filed March 20, 1940 Y Robert E. Mumma Inventors By M Joseph R. Desch and Their Attorney @mu-... N

I April 29, 1952 J. R. DEscH ET AL CALCULATING MACHINE 11 Sheets-Sheet 4 Filed March 20; 1940 @l M, M @n z E M 5 3 m A L ff.; M

Joseph R. Desch and Robert E. Mumma Inventors By M Their Attorney April 29, 1952 Filed Manen 2o, 1,940

J. R. DESCH ETAL CALCULATING MACHINE 11 nshee's-sheet 5 RESET M570/f2 I? /44//1/ .sw/2244 FIG' 40/ 425 90 joseph R. Desch and Robert E. Mumma Inventors Their Attornev April 29, 1952 J. R. DEscH ErAL 2,595,045

CALCULATING MACHINE Filed March 2o, 1940 11 sheets-sheet e FIG. 9A

v gv. 632/ J M372 1L373 E474 575i T T C@ I333 C@ I334 Joseph R. Desch and Robert E. Mumma IZZ 2&3 533 f Their Attorney April 29, 1952 J. R. DEscH ETAL 2,595,045

CALCULATING MACHINE Filed March 20, 1940 11 Sheets-Sheet 7 Joseph R. Desch and Robert E. Mumma Inventors Their torney ApriI 29, 1952 J. R. Di-:scH l-:rAL 2,595,045

CALCULATING MACHINE Filed March 2o, 1940 11 sheets-sheet 8 FIG. 9C

W55 fw YM joseph R. Desch and Robert El Mumma Inventors Their Attorney April 29, 1952 J. R. DEscH ErAL CALCULATING MACHINE 11 Sheets-Sheet 9 Filed March 20, 1940 l Z FIG. 10A

Joseph R. Desch and Robert E. Mumml Inventor: BY M Their Attorney April 29, 1952 J. R. DEscH x-:TAL

CALCULATING MACHINE Filed March 20, 1940 L l M43 745' 753 L Q T T E? l l x I l l i n I l n x l 1 l l l i 11 Sheets-Sheet 10 Joseph R. Dcsch and Robert E. Mumma Inventor! Their Attorney April 29, 1952 J. R. DEscH Erm. 2,595,045

cALcuLATING MACHINE Fned March 2o, 1940 11 sheets-sheet 11 FIG. 10C 204 205" was Joseph R. Dcsch and Robert E. Mumma Inventors Their Attorney Patented Apr. 29, 1952 CALCULATIN G MACHINE Joseph R. Desch and Robert E. Mamma, Dayton, Ohio, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Application March 20, 1940, Serial No. 325,040

136 Claims. l

This invention relates to calculating machines and more particularly relates to an electrical calculating machine that functions to differentially accumulate items solely by the flow of electric energy and without mechanical movement of any parts.

In this novel calculating machine, selected numerical data is entered by means of the differential action of electronic devices into an accumulator comprising a plurality of denominationally grouped electronic devices, the selective operation of which devices during a plurality of data-entering operations causes the accumulation of data. The relative electric condition of the electronic devices in the accumulator, as pertains to their conduction or nonconduction' of electric energy, represents the digit value of accumulated data, which electric condition may be noted by observing the electronic devices or sensed by an electro-mechanical device for visual indication of the data. Neither the diiierential action nor the accumulating action of the machine involves any movement of the parts except for the flow of electric energy therethrough. Data to be entered into the accumulator may be derived from a denominaticnally-arranged keyboard controlling the differential action of a set of electronic devices, or the data standing on the visual indicator may be entered directly into the accumulator electronic devices without the use of keyboardcontrol.

The principal object of this invention is to provide a calculating machine which is much faster in operation than any such machine heretofore known.

Another object of this invention is to provide a calculating machine which is practically noiseless in operation.

Another object of this invention is to provide a calculating machine that can be manufactured (Cl. 23S- 61) at lower cost than machines now known, be-

cause of the fact that accurate operation does not depend upon the manufacture of parts to precise and accurate dimensions, thus eliminating the factor which has contributed greatly to the high cost of manufacture of such machines.

The foregoing and other objects of this invention `are attained by providing an electrical Another object of the invention-is to provide v means for entering data into a numerical accumulator having electronic devices representing denominational digits.

Another object of the invention is to provide a calculating machine accumulator which has in operation no moving parts of ponderable mass.

Another object of the invention is to provide an accumulator of numerical data using electronic devices capable of receiving, accumulating and storing such data at the high speeds associated with purely electrical phenomena.

Another' object of the invention is to provide means for producing a selected number of electric impulses in an electric circuit by operation of a selected number of electronic devices.

Another object of the invention is to provide means to produce a diierentially-selected number of electric impulses at the extremely high speeds associated with purely electrical phenomena.

Another object of the invention is to provide an accumulator for a calculating machine and diierential means for entering numerical data therein, said accumulator and differential means having, in operation, inertia and time factors of those negligible values associated with electrical phenomena.

Another object of the invention is to provide means whereby one group of electronic devices, operated one at a time in sequence, may cause the operation of another group of electronic devices one at a time in the operation sequence intervals of the Erst-mentioned group.

Another object of the invention is to provide an accumulator of numerical data necessitating, in entering diierential data or in withdrawing accumulated data, no movement of the parts except their electrons or ions.

Another object of the invention is to provide means for transferring denominational carryovers in an accumulator of numerical data solely by an electric impulse without physical movement of any parts.

Another object of the invention is to provide means to enter data into the denominational orders of an electronic numerical accumulator in denominational sequence.

Another object of the invention is to provide means for entering data into the denominational orders of an electronic accumulator of numerical data whereby the entry of carry-over data will not interfere with the entry of the selected data or vice-versa.

Another object of the invention is to provide an electronic numerical accumulator wherein stored data is represented by the relative electronic ,state of its parts, with an electro-mechanical means for sensing the stored data without disturbing the electronic conditiouoi "the accumulator. i

Another object of the invention is to provide means for visually indicating the data in a numerical accumulator having the data stored therein in electronic devices.

Another object of the invention is to provide means to set an electronic type of numerical accumulator to represent zero.

Another object of the invention is to provide means to set a visible indicator to "indicate the numerical condition of an electronic type of accumulator.

Another object of the invention is to provide means to set an electronic type of numerical accumulator in accordance with the data set up on a visiual indicator, said entry being made without physical movement of any parts.

With these and incidental objects in view, the invention includes certain novel features of construction and combinations of parts, the essential elements o1" which are set forth in appended claims and a preferred form or embodiment of which is hereinafter described with reference to the drawings which accompany and form a part of this specication.

Of said drawings:

Fig. l is a diagrammatic chart explanatory of the functional relation between theJ several units of the machine.

Fig. 2 is an elevation of a typical key bank, partly broken away.

Fig. 3 is a cross section through the key bank of Fig. 2 on the line 3 3.

Fig. 4 is a side elevation of the step-by-step operating magnet for one denomination of the indicator, the accumulator sensing means driven thereby, and the indicator set in accordance therewith.

Fig. 5 is a section through part of the commutator and Wiper arm assembly of the accumulator sensing means shown in Fig. 4.

Fig. 6 is a wiring diagram of two sets of electronic devices, constituting two denominational orders, and exercising diierential control over the accumulator.

Fig. '7 is a wiring diagram of an enlarged section of a portion of the units denomination set of electronic device shown in Fig. 6.

Fig. 8 is a wiring diagram of the main switch and the manually-operated control circuits for non-indicating, resetting, and restoring operations.

Figs. 9A, 9B, and 9C, taken together, form a Wiring diagram of the units denomination of the accumlator.

Figs. 10A, 10B, and 10C, taken together, form a wiring diagram of the tens denomination. of the accumulator.

Fig. ll is a fragment of a Wiring diagram, similar to Fig. 6, showing the connections for causing entry of data into the accumulator starting with the highest denominational order.

General description The machine embodying the invention may be conveniently considered by sections which are functionally comparable to the key banks, differential actuator, accumulator and visual indicator of a purely mechanical calculating machine. The relation of these sections, as regards their function, is shown diagrammatically in Fig. l.

The calculating apparatus of our invention, which attains the objects stated hereinbeore, includes an accumulator for registering the items entered and for preserving the sum of such items, and such accumulator, broadly considered, comprises a plurality of sets of electron tubes, one for each denomination of the accumulator, each set including an electron tube for each digit of the denomination. The tubes of each set are connected in an endless operative chain so as to be rendered conductive or caused to operate one at a time in sequence, in response to sequences of electric potential impulses impressed on the corresponding denominational input conductor with' which theset of tubes is coupled. The amount registered on the accumulator may be noted by observing which tubes of the sets are conductive.

Means are provided -by which the completion of a sequential chain of operations of a set of tubes in the accumulator will produce automatically anv electric potential impulse in the input conductor associated with the next higher denominational set of tubes, whereby to effect a carry-over from one denomination to the next higher denomination.

As indicated above, the accumulator is actuated by means of impulse sequences impressed upon the denominational input conductors, with which the sets of tubes are coupled. The accumulator is actuated differentially by means of an impulse generator, the output conductors of which are connected to the respective input conductors of the accumulator. Said impulse generator consists of a plurality of banks of electron tubes, one bank for each denomination, and each bank including an electron tube for each of the digits l to 9 inclusive. Each bank of electron tubes is so interconnected that, when operation of 'the' rst tube of the bank is initiated, the remaining tubes in the bank may be caused to operate automatically in sequence, and, as each tube in the bank operates, `or becomes conductive, it generates an electric potential impulse which is transmitted to its output conductor and, hence, to the corresponding input conductor of the accumulator. A series of switches are provided for each bank of tubes, which switches are selectively operable to determine the number of tubes in the bank that will operate sequentially and, thus, determine the number of impulses in a sequence to be generated by the bank and transmitted to the corresponding denomination of the accumulator. These switches of the several banks are selectively controlled so that, on each denominational input conductor of the accumulator, there will be impressed an impulse Sequence, having a number or" impulses in the sequence corresponding to the digit, in the corresponding denomination, of the item to be entered. These switches may be selectively controlled by means of banks of digit keys, upon which the operator sets up the items to be entered.

The apparatus illustrated herein also includes an electro-mechanical sensing and indicating means for rendering visible and readable the data accumulated, which means acts to set the dials automatically with respect to the conductive condition of the tubes in the accumulator banks. The apparatus includes, also, means to reset the accumulator to zero; that is to say, means by which al1 tubes of the accumulator may be caused to cease operation and the zero tubes then caused to operate. The apparatus includes, also, means whereby the sensing and indicating means may be utilized automatically to set the accumulator in accordance with the amount standing on the indicator; that is to say, to cause those tubes of the accumulator to operate which correspond to the reading of the indicator. The apparatus includes,

also, various control devices by which the operation of the apparatus is eiectively controlled.

The disclosed machine has a keyboard of two denominations of nine keys each, representing the units and the tens denominational orders of the decimal system of numbers. These key banks may have set thereon any number from 1 to 99 for entry into the machine in one operation. The section corresponding in function to a differential actuator comprises units and tens denominational orders corresponding to the keyboard, each of which denominational orders acts under control of its associated key bank to enter data into the accumulator, and is purely electrical, having no moving parts except for the key release and the single operation control cooperating therewith. This section is referred to hereinafter as the differential actuator. The accumulator is purely an electrical device and has, in addition to the units and tens denominational orders represented on the keyboard, a hundreds or overow denomination. The accumulator includes a purely electric means associated with each denominational order of the accumulator for transferring carry-overs from one denomination to the next higher denomination. The visual indicator may be set by an electro-mechanical sensing means for each denomination, which means sense, and are controlled by, the datarepresenting electrical condition of the associated denominational order of the accumulator. The principle embodied in the disclosure can be expanded indeiinitelyv in respect to the number of key bank controlled denominations and in respect to the number of overflow denominations and their associated indicator units. The drawings disclose this sectional plan of construction of the machine. The keys, certain controls dealing with special operations, the key release mechanism, and the sensing and the indicating devices are the only mechanically moving elements in the machine. While the drawings show only two denominational orders in the keyboard and three in the accumulator and in the indicator, as many additional denominational orders may be used as desired.

After the keys have been manually set and a starting switch lili! (Figs. l, 6, and 7) has been closed, the data is entered into the accumulator with a speed limited only by ordinary electrical circuit characteristics, such as resistance, capacity, inductance, and ionization time, and not limited by the physical movement of any mechanical part. Data may be entered into the accumulator many times faster than it takes to set up the data manually on a keyboard and to close the starting switch. An approximate time may be computed for the entry of data into such an accumulator if the circuit characteristics are known. In the circuit to be described, the circuit element values are given as typical. ln the particular embodiment based on these values, the longest time required to enter data of two denominational digits, after closing the starting switch, is approximately .0022 second, being the time required to enter the number 99, which is longer than the time required to enter the number 1o.

It is within the purview of this invention to use any of the 'well-known means for controlling the entry of data, other than the manual keyboard described herein; for instance, the switching of the differential actuator circuits may be controlled by any of the well-known methods for sensing data such as that represented on record l areas.

materials by perforatlons, light-controlling areas, electrically-conductive areas, or magnetized The key bank control is used in this embodiment as one example of selective circuitswitching means.

The electro-mechanical sensing and indicat ing means is constantly ready to indicate new totals as new data is entered and is relatively slow in operating compared with the time taken to make an entry of data into the accumulator, yet it will follow the operation of the accumulator and ultimately indicate the amount nally stored in the accumulator, as it is not positively connected to the accumulator, but merely explores its electrical condition until the amount finally stored in the accumulator is sensed, and then stops. If the amount changes, the exploring commences again. The indicator is mechanically attached to and shows the position of the exploring means at any time.

The diierential actuator (Figs. l and 6) is composed of a group of nine grid-controlled gaseous electron discharge tubes for each denominational order. The tubes in each denominational order consist of a starting tube and the nine tubes representing the nine digits 1, 2, 3, 4, 5, 6, 7, 8, and 9. These tubes are arranged in a circuit whereby, commencing with the starting tube, they may be red and rendered electrically conductive one at a time in sequence, one tube being red by the conditions occurring during the starting of conduction in the next lower tube, which lower tube itself lis extinguished as the next tube in the series is rendered conductive. The starting tube in a denominational series is iired by closing the starting switch |00 (Figs. l and 6) to commence the automatic sequential operation. The firing of the starting tube fires the l tube and the iiring of the l tube lires the 2 tube. The firing of the 2 tube fires the 3 tube and extinguishes the l tube. This process continues until the tube representing the depressed key is reached, which tube, upon being fired, cannot fire the tube having the next higher digit value as the anode-energizing circuit of the tube having the next higher digit value is broken by a switch operated by the depressed key. The ring of each tube in a denominational series, except the starting tube, impresses an electric potential impulse upon an output conductor common to all the digit-representing tubes of the denomination. There is one output conductor for each denominational order of the actuator, and each output conductor is connected to the corresponding denominational order of the accumulator, as indicated by reference numbers I 5l! and |53 (Figs. l and 6). The number of impulses impressed on each denominational output conductor in a given operation is equal to the value ofthe depressed key in that denomination.

The denominational groups of the differential actuator are themselves operated sequentially, the firing of the tubes of the group in the units denominational order being completed before the firing of the tubes in the group in the tens denominational order commences, or vice versa, if desired, as will be explained. Timing elements have been provided in each group of tubes of the differential actuator, which elements are operable, when the lower denominations are operated first in the sequegpe, to give a slight pause before the sequential ring of the next higher denominational group of tubes commences, to permit denominational carry-overs to be made to that denomination f the accumulator without interference with the entry of the diierential data. The electric potential impulses, as they occur in the respective output conductors from the differential, actuate their respective accumulator orders, each impulse being so timed as to be reecived by the accumulator before the next impulse is produced.

The accumulator consists of the three denominational orders, units, tens, and hundreds. Each denominational order of the accumulator consists of ten grid-controlled gaseous electron discharge tubes representing the digits (l, l, 2, 3, 4, 5, 6, 7, 8, and 9, which are arranged in a circuit so that they are fired one at a time in endless chain sequence, either by the impulses sent through the output conductor of its associated differential actuator, or by impulses produced by the transfer device, with the exception of the overflow denomination, which is actuated only by the impulses from the transfer device of the next lower denominational order. The carry-overs from one denomiation to the other are made by having an extra electric impulse introduced in the next higher denominational order upon the entry of the next impulse in the lower order after any 9 digit representing tube has been fired in that lower order, said impulse in the lower order also having its regular function of firing the O or zero tube in the lower order. inasmuch as the denominational groups of tubes of the differential actuator are red in sequence, the accumulator orders are added into in the same sequence. In the circuits as disclosed, the pause between operations of the different groups of tubes of the actuator is provided for the purpose of allowing the denominational carry-over impulse, if any, to actuate the next denomination of the accumulator before impulses from the differential actuator actuate it. Such interference between carryover impulses and differential impulses may bev rendered impossible by entering the data into the higher denominational order before entering it into the next lower denominational order, which is done by arranging for the highest order of the differential actuator to be operated first. This may be accomplished by using the units keys (Fig. 1) as tens keys (Fig. 1l), and using the tens keys as units keys and having output conductor |50 lead to the tens bank input terminal of the accumulator and having the conductor |53 lead to the units bank input terminal of the accumulator.

The accumulator, after having data entered therein, has one tube in each denomination remaining in a conductive state, said tube representing the digit in that denomination, of the sum of the accumulated data. Subsequent entries of data into a denomination cause a continuation of the sequential chain firing of the tubes, beginning with the tube having the next higher digit value to the conductive tube. Thus, the accumulator differs from the actuator in that one tube, in each order, is maintained conductive between data-entering operations. Each tube in the differential actuator is fired by the preceding tube, whereas the tubes in the accumulator are fired by the impulses from the differential actuator.

A sensing means is provided for each denominational order of the accumuator, the presence of a zero tube in each denominational order of the accumulator making it possible to sense the zero or cleared condition of a denomination in a positive manner. The normally operative sensing means of each denomination explores the condition of the accumulator tubes through electrically-connected contacts, one by one, until a contact representing a conductive tube is located, whereupon the operation of the sensing means is made to cease and the number which that tube represents is thereby made visible by a number wheel set in accordance with the position of the then stationary sensing means. The sensing means has exploring or wiper arms representing a denomination, which arms when the sensing means is operative, move over the sensing contacts until a conductive tube is sensed in the particular denomination. If the wiper arm is stationary on the contact related to a conductive tube and the tube is extinguished by the entry of data into the accumulator, the exploring movement of the wiper arm will commence and continue until the new contact representing the new accumulation is found.

The accumulator is cleared or set to Zero by extinguishing all the tubes and subsequently ring the zero tubes in each denomination. The sensing means then resume their exploring operation and stop at zero in each denomination because tho-se tubes are now conductive.

If the main supply of electric current be switched off by main switch (Figs. 1 and 8), deenergizing the accumulator and the sensing means before resetting the accumulator to zero, the indicator will still have set thereon the last amount in the accumulator. The accumulator eelctron tubes, being deprived of current will have no tube conductive and therefore will have n0 data therein. Under these conditions, in the event the main supply of current is again turned on by closing switch 919, the accumulator is caused, by the flow of energy through certain wiper arms, set with those previously referred to, 'to render the proper tubes conductive in accord with the data on the indicator. This restoring of data into the accumulator is accomplished automatically, as will be explained.

A non-indicate key switch 423 (l-T'igs. 1 and 8) has been provided so that, upon opening said switch, the accumulator may be operated without the indicator functioning. If the switch 423 is closed after data-entering operations, the indicator will be set in accordance with the accumulated data.

The action of gridecontrclled gaseous discharge electron tubes such as those used in the differential actuator and accumulator, is well known. An electric potential of sufficient magnitude impressed between a cathode and an anode in gas-filled envelope is controlled by an intervening grid element which is normally provided with a negative bias potential with relation to the cathode so as to prevent the flow of electrons to the anode. If the biasing grid potential is reduced to a point where it is no longer in control of the emission of electrons from the cathode, current will fiow at once through the tube from the anode to the cathode and in so doing will ionize the inert gas within the tube. rThe ionization of the gas within the tube causes increase in the fiow of electrons from the cathode to the anode and renders the grid incapable of further blocking the electric ow. This flow, once started, will continue even though the grid be restored to its controlling bias potential, and will not cease until the cathode-anode current is interrupted by some other means. When the gas in the tube is ionized and the electron flow has started, the tube is said to have been fired, discharged, or rendered conductive. This is also called the operating condition of the tube and whenever, in this specification and the claims, reference is made to causing an electron tube to operate, it is intended to mean the bringing of such tube to the condition of maximum conductivity. The conductive tube may be extinguished, or rendered non-conductive, either by adjusting the cathode capacity and resistance so that for an instant, as the capacitors are charging, there is no flow of current from the anode, or by shutting off the potential completely. Under these conditions the grid, if at controlling bias potential, resumes control. Both of these phenomena are used in the disclosed machine, as will be explained. Ordinarily the bias potential of the grid with relation to the cathode is not kept at a hairtrigger point, but at a substantial biasl thus rendering the tube more stable and unresponsive to slight fluctuations of potential of the grid.

The automatic sequential firing of the tubes in the diiferential actuator is accomplished by placing a high resistance in the cathode supply circuit of each tube, which causes an abrupt positive rise in potential of the cathode of a tube as it res, and this abrupt rise in potential is utilized through interconnecting circuits to extinguish the tube of next lower digit value in the series by temporarily raising its cathode potential above the potential of the anode, and, by the same positive potential rise, to destroy the grid control of the tube having the next higher digit Value, causing it to re unless it be cut out by switch means operated by a digit-representing key.

In the accumulator, the same phenomenonthe 'rise in potential of the cathode when the tube fires, caused by placing a high resistance in the cathode supplyis used to extinguish the tube having the next lower digit value in the series, as is the case with the differential actuator, and to weaken the grid control of the tube having the next higher digit value by reducing its bias to the trigger point so that the next potential impulse from the differential actuator, which impulses are common to all the tubes of the accumulator series, will cause only the tube with the weakened grid bias to fire. More detailed explanation will be given on this subject as the accumulator is describe more particularly.

The digit keys, by operating switches, control the stopping of the firing of the tubes in each of the differential groups after predetermined numbers of tubes have been iired. As each tube is red it produces, by the rise in its cathode potential, an electric impulse in a conductor common to al1 the differential actuator tubes in the denomination, which impulse isconveyed to the corresponding order of the accumulator, which causes the firing of the tube next in numerical order. Thus, except for the release of the keys after the entry of the data and except for the means to prevent a repeat entry while the keys are still depressed, there are no movements of mass involved in data-entering operations except themass of electrons and ions causing the electric current. The only factors which limit the speed of the entry of data are electrical in nature and are placed in the circuit fory the proper timing of the impulses and ring of the electronic devices.

The speed of the actual entry of data into the accumulator is so extremely rapid that the time of making such an entry is negligible in comparison with the duration of the manual movements necessary to press the starting key. The

time lapse between the pressing of the starting button and the consequent firing of the tubes in the differential actuator and the accumulator may be as short as .001 second for the entry of a single digit. From this it will be apparent that the speed of making an entry into the accumulator is extremely fast in comparison to the speed with which the data may be set up either by manual keys as shown in this embodiment or by other more rapid data entry control means such as mechanically-sensed, electrically-sensed, or light-sensed records, which data entry control means have been mentioned as within the purview of the disclosure.

The diagrammatic representation shown in Fig. 1 illustrates the denominational groups in the differential actuator, the accumulator, and the indicator. These groups may be added to as desired. There may be more than one overflow denomination if desired,` but there must be one accumulator order for each denomination of the differential actuator and one indicator for each denomination of the accumulator.

The principle of the invention, as set forth in this disclosure, is embodied in a machine having certain electric supply potentials and electronic devices of certain electrical characteristics. In balancing the circuits, resistors and capacitors having a xed relationship with one another are used. Electronic devices or potentials of different characteristics may be used without departing from the principle of this invention, merely by using different values of resistance and capacity to obtain the relationship disclosed herein.

The keyboard The keyboard consists of a units denomination key bank 6l (Fig. l) having nine digit keys 62 (Figs. 1, 2, 3, and 6) and a tens denomination key bank 63 having nine digit keys 86 (Figs. 1 and 6). The keys in each bank are of similar construction and a description of the keys in one bank will be suflicient for an understanding of all the keys.

Each key has a stem 66 (Figs. 2 and 3) slidably mounted in alined holes in a top plate 64 and a bottomplate 65 of a unitary key frame, said plates being spaced and fastened together by transverse vertical webs 13 and 14 (Fig. 2) each of which has laterally projecting ears 61 to engage side plate members 68 and 69 (see also Fig. 3) of the key frame. Each keyis provided with a restoring spring 10 (Fig. 2) which engages vthe bottom plate 65 and is contained in-a slot 1I in the key stem where it is retained by projections 12. As a key is depressed, the spring compresses against the bottom plate 65, giving the key an upward restoring urge. The keys are limited in their upward motion by a shoulder on the key stem 66 striking the top plate 611., A key locking plate 15 (Figs. 2 and 3), having clearance holes 16 for each key stem, is slidably mounted in clearance holes in the webs 13 and 14. The locking plate 15 is urged to the left, as shown in Fig. 2, by spring 11 until the edges of the key clearance slots contact the key stems. As a key is depressed, the locking plate is forced to the right by a camming surface on the key stem, until notch 18 allows the locking plate to move to the left, locking the key in depressed position. By chamfering each of the notch edges, the action of the key bank is made flexible, causing any depressed keys in the bank to be lrestored when another key in the bank is depressed. Each key stem has inserted therein an insulating web formed of two pieces 19 and 90 (Fig. 3) having ears projecting into slots in the key stems 66 and into guiding slots 9| in the side plate members 68 and 69, so that the insulating web pieces slide up and down with the keys. On each web are four contacts 82, 83, 84, and 85 (Figs. 2 and 3) each of which contacts in the up position can close a circuit between one pair of switch points and in the down position can close a circuit between another pair of switch points. These switch points are supported by the side plate members 68 and 69. Therefore, by the depression of a key, four circuits may be broken and four circuits may be closed. The invention uses but three of these four available pairs of switch points, the description of this key bank being given to illustrate one way in which multiple switching may be accomplished by a single key. A key release solenoid 26| for the units bank of keys (Figs. 2 and 6), when energized, moves lever` 263 counter-clockwise, around pin 264, to move the locking plate 'l5 to the right and release a depressed key. A similar solenoid 262 causes the release of any depressed key in the tens bank of keys. There is one gas-nlled electron tube |55 (Fig. 6), similar to those already described, for controlling the operation of both solenoids 26| and 252. The control tube |55, when fired, energizes a solenoid |49 to close the nor'- mally open switch |41, which supplies the grounded solenoids 26| and 262 with 45 volts positive potential, causing these solenoids to become energized and operate their armatures and thus release any depressed digit keys.

The circuits entering into the operation of the control tube |55 will now be considered.

As the main switch 90 (Figs. 1 and 8) is closed, terminals'9l, 92, 93, and 94 are impressed, respectively, with the following electrical potentials: 170 volts positive, 45 volts positive, 6.3 volts positive, and 150 volts negative.

Terminal 93, which has a potential of 6.3 volts positive at this time, supplies the current to heat the cathode 265 of control tube |55 and is shown grounded in Figs. 6 and .7 through a typical heater filament symbolical of the heater laments of all the tubes. The heater circuits from the terminal 93 to the tubes have been omitted because they would tend to obscure oth er circuits in these figures.

When the main switch 90 is closed and terminal 94 has a 150-Volt negative potential applied thereto, the conductor 95 assumes this potential. Grid 26'! of the control tube |55, when no digit keys have been depressed, assumes a normal bias of 150 volts negative by being' connected to the 150-volt negative conductor through resistor 269 of 250,000 ohms and the paralleled resistor and capacitor comprising resistor |58 of 100,000 ohms and capacitor 620 of .005 rnicrofarad.

The cathode 265 of the control tube |55 is connected to ground. With the grid 261 at a potential of 150 volts negative and the cathode 265 grounded, the tube |55 will not re.

When the main switch 90 is closed, the l'IO-volt positive potential of terminal 9| will not be applied directly to the plate 266 of the control tube |55. However, when the starting switch is closed the plate 266 has 170 volts applied thereto through a circuit which extends from the terminal 9|, over 'closed contacts of the starting switch |00, through resistor |48 of 300 ohms and the solenoid |49. To slow down the application of this potential to the plate and prevent the possible firing of the tube by the sudden application of this potential when the starting switch is closed, a capacitor 26| of .l inicrofarad is connected from a point between the resistor |48 and the solenoid |49 to the 150-volt negative line 95.

When no digit key has been depressed, the closing of switch after switch 90 has been closed, in addition to supplying the plate potential to tube |55, also supplies a. positive potential to its grid 267 through switch |46, resistor |9| oi 200 ohms, resistor |62 of 100,000 ohms, through the contact arms as |03, |94, closed on their upper contacts since no keys are depressed, through the conductor |52, common to both denominations, and resistor 268. This V10-volt positive impulse on the grid 261 changes the potential of the grid from negative to positive and causes the tube |55 to re and become conductive, the current flowing through the plate circuit of the tube energizing solenoid |49, which operates and closes the circuit to key release solenoids 26| and 262, as explained above, without any result as far as the digit keys arev concerned, as none were depressed.

However, if keys have been depressed-for exa1np1e,'the 5 key in the units bank and the 70 key in the tens bank-the 170-volt impulse introduced on conductor |52, by closing starting switch 00 after the main switch 90 has been closed does not directly affect the grid 26?, but is switched so that the 170 volts positive impulse is impressed on the grid of the starting tube |69 of the units denomination, through line |60 and resistor ||5 of 400,000 ohms, iiring that tube, as will be explained, to start the sequential ring oi the tubes in the units bank. Tube |09 remains conductive until its plate circuit is interrupted by opening switch |00 or switch |46 and as long as this tube remains conductive it is impossible to start the sending of a second group of impulses over output conductor |50. After the ensuing sequential firing of the 1, 2, 3, 4, and 5 tubes of the units bank, and the starting tube the n10, U20, n30, 40,1: n50n 60u and 70 tubes of the tens bank, a positive cathode potential impulse caused by ring the 70 tube is switched onto the common conductor |52 by the key-operated switch |6| (closed by depression of a key in the bank of highest order) to fire the control tube |55, the firing of which tube causes the energization of the solenoid |49 and thereby the energization of solenoids 25| and 262 to cause the release of the keys. The starting switch |00 must be held closed until solenoid |49 is energized, but this interval is so short that it is practically impossible for the operator to withdraw pressure from switch |99 before solenoid |49 is energized. When the solenoid |49 is energized, switch |46 is opened to disconnect the common 'conductor |52 and conductor |44, which supplies plate potential to the tubes of the differential actuator, from the source of potential to which they have been connected by the closing of the starting switch |00. By thus removing the potential from the plates of the tubes, any conductive tube will be extinguished and none of the tubes can be rendered conductive thereafter until switch |46 is again closed and by switch |99 being again opened and closed, so that any impulses which would be generated by shifting contacts as |04, |43, |5I, |6|, and |9| when the keys are restored to undepressed position with the starting switch |00 closed, would not cause a misoperation of the tubes.

When the 70 key is depressed, as described above and shown in Fig. 6, switch |6| connects the point 212; that is, the grid of control tube |55, and common conductor |52 to ground through the resistor 259 of 100,000 ohms, the resistor 210 of 25,000 ohms in parallel with a capacitor 213 of .02 microfarad, through the tens denomination output conductor |53 and the resistor 21| of 5,000 ohms. This causes the potential of the point 212 and grid 201, which are connected to the 15G-volt negative conductor 05 through the resistor |58 of 100,000 ohms and capacitor 620 of .005 microfarad in parallel, to drop from 150 volts negative to approximately 84 volts negative, which drop is not sufficient to cause the tube to fire or be conductive. If the circuit just traced were the only circuit in the tens bank, the point 212 would assume the potential of about 84 volts negative, but circuits associated with the 10, U20, 30, H40, 50, M60, and H809 tubes are also included in the tens bank. These circuits form parallel paths which extend from the 150 volts negative conductor 95 through resistors 638, G13, 653, 653, 000, GSi, and 61|, through switches similar to ESI, (closed on the upper contacts since the keys are elevated) through resistors similar to 260, through resistors and capacitors in parallel similar to 210 and 213, to the tens denominational output conductor |53 and thence through resistor 21| to ground. These parallel paths between the 15G-volt negative conductor 95 and output conductor |53 cause the eiective resistance of this part of the circuit to become smaller and raise the negative potential of the tens output conductor |53 and also raise the negative potential oi the point 212 slightly above the 84 volts negative mentioned above. This negative increase in potential of point 212 will not affect the operation of the tube |55. When the '10 tube res, its cathode will acquire a positive potential which, through resistor 259, will cause the potential of the common conductor |52, and point 212, to change so that the potential of the grid 251 will become about 21/2 volts positive and this will cause the tube |55 to fire and become conductive. The manner in which the potential of the cathode of the 70 tube is raised to a positive value to change the potential of the grid 261 from negative to positive will be made clear during the description of the operation of the differential actuator. The ring of tube |55 will result also if a key in the units denomination bank is depressed and no key in the tens denomination bank is depressed, as the last tube to re in the units bank will have its cathode positive potential impulse shunted around the tens bank on conductor |52 to the grid 251 of the key release control tube |55 instead of to the starting tube |511 of the tens bank, by reason of all the key switches in the tens bank being in normal position.

Diyferential actuator In describing the diierential actuator, as regards its electrical operation, it is necessary to trace the flow of electric energy through the circuits. As the operation of the differential actuator is dependent on relative values of the electric potentials, resistors, capacitors, and the electron tube constants, for the timing and the sequence necessary in producing the differential action, actual values will be given as an example. These values are given to show how the difierential operates and should not be considered the only set of values which can be used. The values used are determined by the input voltages selected, by the type of electron tube selected,

and by the speed of operation needed. It should be evident from the explanation which follows that certain of the time factors involved result from the proper choice of these values. With the values given here as an example, the impulses for the number 99 may be impressed on the output conductors |50 and |53 to the accumulator, as has been said, in about .0022 of a second after the starting switch |00 (Figs. l and 6) is closed, and the number l may be impressed on the output conductor |50 to the accumulator in about .0003 of a second. If there were ve denominational key banks, the number 99999 could be impressed upon the ve output conductors to the accumulator in about .0058 of a second. Inasmuch as it is necessary for the accumulator to respond to the impulses from a given denomination of the differential actuator one by one, it is app-arent that its speed of response is somewhat higher than that of the actuator. The extremely high-speed production of differential impulses and operation of an accumulator by the imp-ulses are due to the fact that they are accomplished solely by the ow of electric current without movement of ponderable mass.

The wiring of the circuits of a two-denomina-v tion dilerential actuator is shown in Fig. 6. An enlarged section of part of the circuit is shown in Fig. 7, to which reference is principally made in the following explanation. i

In giving the explanation of operation of the sequential iiring of the tubes in the differential actuator, the rst portion of the units bank (Fig. 7) is used as an example. This portion shows starting switch |00, the l and f2 digit keys 62, the tubes |2| and |28 representing digits l and 2 respectively, the units denominational order starting tube |09 for starting differential operation of the digit tubes when a key is depressed in this order, the key release control circuits, the circuit breaker switch for single operation control, and the various circuits coordinating these elements.

The conditions resulting from the firing of the starting tube |09 are such that they have no effect on the digit-representing tubes except to fire tube |2| representing the digit 1. The method of ring the 1 tube by a starting tube to commence the differential action is used as a convenient way of impressing a uniform ring impulse on the grid of the 1 digit-representing tube |2|, in operations wherein a key of that i denomination is depressed. It is to be noted that the starting tube could be replaced by any other means that would 'lre the l digit-representing tube. The sequential firing of the tubes is so rapid that the ring of the l digit-representing tube vcannot be done reliably by the switch |00 alone because of the possibility that the operator might vibrate switch |00 in closing it, thus giving more than one ring impulse to the digit-representing tube |21 before the keys are released and causing the firing of the selected tubes more than once, which would result in an error in the entry of data. The starting tub-e is not extinguished and therefore cannot be red again until the data-entering operation is completed and all the tubes are deprived of energy by the opening of switch |45. It will be explained later how the digit tubes are extinguished after firing either by the action of the next tube firing or by the completion of the data-entering operation causing switch |46 to open.

Each of the digit-representing tubes |2| and |28 has associated therewith a circuit which connects the 14o-volt negative conductor 95 to the ground. The circuit for the 1 digit-representing tube is representative and is traced as follows from ground, through resistor |26 of 5,000 ohms to point |24 `and output conductor |50, through resistor |25 of 25,000 ohms and capacitor |35 of .02 microfarad in parallel to point |23, through resistor |30 of 100,000 ohms, through switch |64 of the unoperated digit key to point |20 and through resistor |3| of 100,000 ohms, to the 150- volt negative conductor 95. The cathode for the "1 digit-representing tube |2| is connected in this circuit at point |23, and the grid for the 2 digit-representing tube |28 is connected, through resistor |51 of 500,000 ohms, to the point |29. The connection of the cathode of the tube of lower digit value to the grid of the tube of the next higher digit value by means of circuits such as this one enables the ring of one tube to cause the next tube to re in sequence.

Although but two digit-representing tubes are here considered, the explanation given will serve for the whole denominational bank of nine tubes, as the resistors, capacitors, and bias potentials used are of the same values. The firing of the tubes occurs in so short a period of time, ranging in the ten-thousandths of a second, that the transient changes in voltage cannot be measured with absolute certainty, and therefore, although the use of the resistors, capacitors, and the potentials of the electric supply lines of the values as given will result in accurate operation of the machine, the potential fluctuations in the circuits as stated should be deemed approximations and are `given chieiiy to explain the theory of operation.

In the explanation of the operation of the differential actuator as made in connection with Fig. '7, it will be assumed that the 2 digit key 02 has been depressed manually-from a position shown by the full lines to the position shown by the dotted lines and the switches |04, |43, and |5| have been moved from the fullline position to the dotted-line position.

As mentioned previously, when the main switch 90 (Figs. l and 8) is closed, terminals 9|, 92, 93, and 94 are impressed with the following electric potentials, respectively: 170 volts positive, 45 volts positive, 6.3 volts positive, and 150 volts negative.

These terminals, also shown in Figs. 6 and 7, supply the necessary electric energy to operate the differential actuator.

Terminal 93 of 6.3 volts positive, as has been mentioned, supplies the current to heat the cathodes of all the electron tubes in the differential actuator and accumulator and is shown grounded in Figs. 6 and 7 through a typical heater filament symbolical of the filaments of all the tubes. 'I'he heater circuits from the terminal to the various tubes have been omitted for the reason that they would tend to obscure the other circuits to be described. Heater elements, which have been symbolically shown in each tube, are connected to terminal 93 and become heated when the main switch 90 is operated.

When the main switch 90 is closed andthe potential of 150 volts negative is applied to conductor 95, the grid of the starting tube |09, which is connected to this conductor through resistor |05 of 100,000 ohms and capacitor of .005 microfarad in parallel,.point |05, and resistor I5 of 400,000 ohms will assume a negative potential ol approximately 150 volts. At the same time, the potential of thecathode |08 of the starting tube |00 and the point in., which are connected to ground through resistor ||6 of 25,000 ohms, will assume a slight negative potential while the capacitor lll is charging, being connected through capacitor of .00005 microfarad, to point H0, through resistor |45, of 400,000 ohms to point |00, which is located between resistors |ll| of 75,000 ohms, and |42, of 100,000 ohms, connecting the 15G-volt negative conductor 05 with ground. When the capacitor has become charged and current no longer iiows in this circuit, the point |4 will be at ground potential. The slight negative potential rise of the cathode |08 will not cause the tube- |09 to be fired, because the grid |07 at this time has a potential of 150 volts negative and the characteristics of the tube are such that it will re and conduct current :from the anode to the cathode only when the potential of the grid exceeds, in a positive sense, a potential value of 15 volts more negative than that of the cathode.

Upon closing the starting switch |00 after the main switch has been operated, the l70-volt positive terminal 9| is connected to the point |06 in the circuit from the 15G-volt negative conductor to the grid |01, which connection is from terminal 9|, through starting switch |00, through the normally closed switch |40, resistor |0| of 200 ohms, resistor |02 of 100,000 ohms, switch |03 in its normal unoperated position, conductor |52, switch |04 in its operated position, and conductor |00 to the point |00, to which the grid |01 is connected. This application of 170 volts positive potential to the point |06 will cause the potential of the grid |01 to change from 150 volts negative to about 9 volts positive with respect to the grounded cathode and will cause the starting tube |09 to nre and be conductive. The capacitor of .005 microfarad in the circuit connecting grid |07 with the 15G-volt negative conductor acts to slow down the application of the ring voltage to the grid l0?.

When the starting switch |09 was closed, as noted above, it also connected the plate ||0 of f the starting tube |00 to the 170-volt positive terminal through the circuit over the closed switch |00, over the normally closed switch |46, and resistor |0|, and from this point over conductor |44, capacitor ||2 of .005 microfarad in parallel with resistor i i3 of 400,000 ohms, to plate l0.

As the starting tube rires, it allows electrons to flow. from the cathode |08 to the plate H0. The ow of current through the tube |09 is not limited by the 400,000-ohm high resistance ||3 until capacitor 2 becomes charged, at which time the resistor ||3 becomes effective to reduce the plate-cathode current and also to reduce the potential of cathode |00. The potential drop across the tube |09, when conductive, is about 15 volts as is usual in gaseous electron tubes of this type. This makes point ||4 have, after the ring of tube |09 and as capacitor ||2 starts to charge, a potential of about Volts positive with respect to ground. When resistor ||3 assumes the current load as the capacitor |I2 becomes charged, the potential of the plate ||0 drops to about 25 volts positive with respect to ground, and the cathode |08 and point ||4 assume a potential of about l0 Volts positive with respect to ground. After the rst surge of current from plate ||0 to cathode |08 in tube |09, the resistor ||3 makes the current i'iow very small. Resistor ||6 limits the cathode current flow Abefore resistance ||3 takes effect and acts 17 to make the potential of cathode |08 high while capacitor H2 is charging. Resistors |05, of 100,000 ohms, resistors and |02 totaling 100.200 ohms, and resistor H5, of 400,000 ohms, limit the grid current. It is seen, therefore, that, as tube |09 fires, a momentary voltage surge of approximately 146 Volts positive is impressed across the .00005 microfarad capacitor H1 to point H8 and causes a positive Voltage impulseof about 145 Volts to be to be impressed at said point H8. Point H8 is normally at a potential of 64 volts negative with respect to ground, being connected through resistor |05 of 400,000 ohms to point |40 between resistor 10| of '15,000 ohms and resistor |42 of 100,000 ohms connecting the ground conductor with the 150-volt negative conductor 95.

The grid of the 1 digit-representing tube is connected, through resistor |56 of 100,000 ohms, to the point H8 and assumes its normal poten-` tial of 64 volts negative, which changes to a posi'- tive potential of about 82 volts when the starting tube fires and impresses the positive potential surge of 146 volts on point H0. When the main switch 90 is closed and the 150 volts negative potential is applied to conductor 95, current will ilow in each of the circuits associated with the digit-representing tubes, such as the one traced earlier herein from the 15G-volt negative conductor 95 through resistor |3 l, point |29, switch |00 in normal position, resistor |30, point |23, paralleled resistor |25 and capacitor |35, output conductor |50, point |24, and, through resistor |20, to ground. The potentials of the points |23 and |29 will become fixed after capacitor |35 becomes charged, and the only current flow will be that determined by the resistors. Under these conditions, the point 23 and cathode |20 of the l digit-representing tube connected thereto will assume a potential of about 19 volts negative, point |20 and the grid |32 of the 2 digit-representing tube connected thereto will assume a potential of 84 volts negative, and point 24 and the output conductor |50 connected thereto will assume a potential of 3.2 Volts negative.

When the starting switch |00 is operated after the main switch 90 is closed and the 2 digit key is depressed, the 170-volt potential is applied to plate |22 of the l digit-representing tube through a circuit traced from terminal 9|, operated starting switch |00, switch |45, through resistor |0| of 200 ohms, conductor |40, andv through operated switch |43.

With the grid |9 of the 1 digit-representing tube normally at the same potential, 64 volts nega-tive, as is point H8, and the cathode |20 at a potential oi 19 volts negative, the gaseous triode 1 digit-representing tube 2| is kept from ring,

When the 14S-volt positive potential impulse, caused by the ring of the starting tube |09, is impressed upon the grid H0 of the 1 digit-representing tube |2|, it is apparent that grid H0 will become temporarily about 82 volts positive with respect to ground, or 101 volts positive with respect to the 19-volt negative cathode |20, and the tube |2| will lire. The voltage impulse at point H8 which res tube I2! is kept from grounding by resistor |45 of 400,000 ohms. Resistor |56 of 100,000 ohms in series with resistor |45 limits the grid current of grid H9. l

When the tube |2| res and the gas therein becomes ionized, the internal resistance ofthe tube dropsand the potential difference between plate-l 22 and cathode |20 drops to about 15 volts,

so that cathode 20 and point |23 will have a potential slightly less than volts positive with reference to ground. It should be noted that the resistor |0| of 200'ohms in the plate circuit is much smaller than the resistors |25 and |20 totaling 30,000 ohms in the cathode circuit and the voltage drop across the resistor |0| will have but little eiect in changing the potential of plate i 22 when the tube hres.

At the moment the tube fires, the current in the cathode circuit between points |23 and |20 momentarily will be principally through the capacitor |35 and very little will ow through the resistor |25, so that there will be a very small voltage drop across this resistor and points |23 and |24 will have about the same potential= |55 volts positive with respect to ground. As the capacitor |35 becomes charged, more current will iiow through resistor |25 and the potential drop across the resistor will cause the point |24 to have a more negative potential than point |23.. The rise of the potential of the cathode |20 toward 155 volts positive will cause the grid |32 of the 2 digit-representing tube 28, which is connected to point |23 through resistor |30, unoper ated switch |50, point |29, and resistor |51, to change from its normal negative potential of 84 volts to a positive potential of approximately 2.5 volts. This change in potential of grid |32 will not cause the 2 digit-representing tube to lire immediately, because the point |24 and conducn tor |50 have about the same potential as point |23 when the capacitor |05 begins to charge and the cathode |21 of the 2 digit-representing tube, which cathode is connected to output conductor |50 by the resistor |31 and capacitor |30 in parallel, will have a potential change similar to that of grid |32 and will retain the effective biasing potential difference between the grid |32 and cathode |21 of the 2 digit-representing tube so as to prevent the tube from firing immediately. As the capacitor |35 becomes charged and current begins to fiow in resistor |25, there will be a potential drop across this resistor which. will increase as the capacitor becomes charged and more current iiows through. the resistor. Underthese conditions, the positive potential of point |20 and the output conductor |50 will decrease as the drop across the resistor |25 increases, while the potential of the point |23 remains unchanged, so that, while the potential of the grid |32 remains at 2.5 volts positive, the potential of the cathode |21 will drop below 17.5

volts positive, at which time the potential of grid |32 will exceed, in a positive sense, a potential value 15 volts more negative than that of the cathode |21 and the 2 digit-representing tube |28 will ,fire and be conductive.

Through the same circuit as described above in connection with the l digit-representing tube, the plate of the 2 digit-representing tube has impressed thereon a potential of about `volts positive. The cathode circuit for the 2 digit-representing tube is similar to the one for iires, its cathode |20 is at 155 volts and the surge 

